Red, green and blue light emitting diodes (LED) capable of realizing high luminance and white light were developed, based on development of metal organic chemical vapor deposition and molecular beam growth of gallium nitride (GaN).
Such LEDs do not contain environmentally harmful substances such as mercury (Hg) used in conventional lighting apparatuses such as incandescent lamps or fluorescent lamps and thus advantageously have superior eco-friendliness, long lifespan and low power consumption, thus being used as alternatives of conventional light sources. The key factors in competitiveness of such LEDs are to realize high luminance, based on chips with high efficiency and high power and packaging technologies.
In order to realize high luminance, an increase in light extraction efficiency is important. A variety of methods using flip-chip structures, surface texturing, patterned sapphire substrates (PSSs), photonic crystal techniques, anti-reflective layer structures and the like are being researched in order to increase light extraction efficiency.
In general, a light emitting device may include: a light emitting structure including a first conductive type semiconductor layer, an active layer and a second conductive type semiconductor layer disposed on a substrate; a first electrode to supply a first power to the first conductive type semiconductor layer; and a second electrode to supply a second power to the second conductive type semiconductor layer.